The present invention relates to packaging that is made of plastic, and which comprises a dish or cup-shaped container, and a cover that can be installed on the container and that is intended to re-close the container once it has been opened for the first time, and means operable in conjunction with the container and the cover to indicate the original sealed state of the container.
A large number of packaging types of this kind, that are of plastic, are in wide-spread use. Without exception, these known packaging have thin walls and are manufactured from plastic film by deep drawing, by blow moulding, or by injection moulding techniques.
Mainly when packaging food stuffs, but also when packaging articles of everyday use, manufacturers place great value on the fact that after buying a filled packaging from the shelf of a retail store, the consumer has packaging that still bears the original seal. Packaging that has not been opened provides assurance with respect to hygiene and the quality of the food stuff that has been packaged, and provides an assurance that the packaging contains the specified number of items in the case of non-food articles, etc.
In order to ensure the original sealed state of the packaging, when such plastic packaging is used, special measures are required ("original sealing"), for which a number of different construction principles can be used in practice.
Thus, it is known that in so-called blister packs that a blister card or a back that is of plastic can be sealed or welded onto a deep-drawn plastic part. In a similar way, when, for instance, chicken salad or similar food stuffs that spoil easily are packaged, a sealing plate of aluminum or of the same material as the container can be sealed onto a container that is moulded from plastic; the sealing plate is so installed by the action of pressure and heat that, as a rule, it can be easily removed and after the package has been opened for the first time, it can no longer be sealed to the container. Blister packaging that is damaged or destroyed when it is opened for the first time, or a sealing plate that has been removed at least partially, provide the consumer with an unmistakable indication that the packaging is no longer in the original sealed state. Whereas when the original sealed state is maintained, the contents of the package are properly protected, temporary closure of the packaging after it has been opened for the first time is no longer possible. In those cases in which temporary re-closure is required, a dedicated re-closing cover must be enclosed with the packaging, and this entails additional expenditures with respect to both cost and packaging means.
In addition, when a sealing film of aluminum or another material that is not the same as the material used for the container is used, the packaging then becomes two-material packaging, which is at odds with the efforts being made to achieve simple recycling of packaging material that is becoming increasingly important today.
More favourable conditions with respect to the re-use of packaging material that has been used result in the case of other known plastic packaging that consists of a plastic container or lower section and a plastic cover, when the original sealed state is ensured by the use of a self-adhesive label that is affixed to the cover and to the container. Other embodiments are used, in which the edge of the cover is so configured that, together with the edge of the container, it is sealed vertically, so tightly that the cover cannot be removed from the container unless one uses a specially provided opening that, in the original sealed state, is closed off by a label or a plastic strip. The fundamental disadvantage of such solutions lies in the fact that, on the one hand, it is difficult to so configure a self-adhesive label that it cannot be removed and then re-attached if sufficient care is used, and, on the other hand, a different type of material is introduced into the packaging by the use of such a label.
There is also plastic packaging in which a cover is slipped onto the container, this then snapping into position as a result of appropriate configuration of the container and/or the cover edge. Only after removal of a lower cover edge area that is joined to it through a nominal break line can the cover be removed when the container is opened for the first time. In order to prevent such an original closure from being defeated by a user in that the container wall is pressed inward (elastically), until the cover can be removed without tearing off the lower edge section of the cover, the container must have relatively thick walls. It is true that such containers are acceptable for pharmaceuticals or cosmetics, but because of the costs involved they are not used for packaging a number of consumer food stuffs.
Finally, it is known that when such plastic packaging is used, the cover can be provided with a tear-off tab that is torn off or removed along a defined nominal break point or line when the container is opened for the first time. As a rule, covers that are configured in this way can only be produced by injection moulding; they are too costly for many single-use items.
For this reason, it is the object of the present invention to create plastic packaging that provides a solution to the problem of the so-called original sealing and which is as reliable and cost-effective as possible.